Historical clue formulations

• Any singer of the 1973 #1 hit "Love Train" — 2018-02-12
• Any of the singers of the 1973 hit "Love Train" — 2012-06-21
• Any of the singers of the 1973 #1 hit "Love Train" — 2012-02-21
• Any member of a 1970s R & B group — 2007-09-23
• One of a 70's R&B group — 2000-05-11